1. Field of the Invention
The present invention relates to a communication terminal, such as a cellular phone, that enables to be connected to an external apparatus such as a personal computer, and a communication system and a communication method. The present invention particularly relates to a communication terminal that enables to be used as a communication modem when the communication terminal is connected to an external apparatus by USB (Universal Serial Bus) which is a bidirectional communication interface.
2. Description of the Related Art
A function is presently available that permits a portable communication terminal such as a cellular phone to be connected to a personal computer (hereinafter referred to simply as a PC) via a USB port, and that controls the portable communication terminal to serve as a communication modem (see, for example, JP-A-2003-298762.).
In order to provide this function for a PC, and to prepare for the employment of the portable communication terminal as a communication modem, a modem driver must first be installed in the PC.
A modem driver is provided for a PC using one of the following first, second and third methods.
According to the first method, a modem driver is provided through a recording medium such as a CD-ROM which is packaged with a portable communication terminal.
According to the second method, a PC that can access the Internet using communication means other than a portable communication terminal, e.g., by using a fixed, dial-up telephone line connection, is employed to download a modem driver from a server.
According to the third method, when a portable communication terminal is connected to a PC, the PC automatically accesses an FTP server on the Internet and obtains driver version information. Then, if a compressed file for a driver program has been stored in memory, the driver version information for this file can be read and compared with driver version information obtained from the FTP server, and the newer version of the two can automatically be installed in the memory of the PC.
JP-A-2003-298762 is referred to as a related art.
However, when these methods are employed, the following disadvantages adversely affect their usefulness.
For the first method whereby a recording medium, such as a CD-ROM, is included in a package, there is disadvantage that expense for packaging the recording media is needed and that a user cannot update the modem driver to the latest version.
For the second method whereby a modem driver is obtained through the Web by a PC that accesses the Internet, there is disadvantage that the modem driver can not be downloaded when the PC has no access to the Internet.
For the third method whereby access to the Internet is always required to confirm the driver version when a portable communication terminal is connected to a PC, there is disadvantage that it is wasteful in time and inconvenient to establish a communication link for this purpose, since driver versions are not so frequently updated.
Furthermore, the browser of the portable communication terminal is activated each time a link is established. Thus, there is disadvantage in convenience that even when no updated driver version is available, the activated browser must be closed in order for a user to do other tasks each time the link is established.